Legend:
In blue, conservation of amino acids from YHT34.5HL in the reshaped antibodies in order to restore the hydrophobic core
formed by residues 28, 35, and 39 [2].
The first mutation S28>F regains the prior affinity of CAMPATH-1H for CD52.
The second mutation S35>T ensures CAMPATH-1H to retain the highly specific and
tight binding characteristic of the rat antibody.

The humanization of CAMPATH-1H was made by using the Kabat CDR (green) and FR (red) delimitations.
Interestingly, the analysis using the IMGT unique numbering [3, 4, 5] shows that:

The two necessary amino acid changes, S28>F and S35>T, are in the CDR1-IMGT. These positions were previously considered
as Kabat FR1. According to the IMGT unique numbering, positions 27 to 38 should have come from the 'rat' sequences,
therefore preserving the specificity.

The positions 66 to 78 belong to the FR3-IMGT (C" strand). These positions were previously considered
as Kabat CDR2. According to the IMGT unique numbering, positions 66 to 78 could have been
kept from the 'human' sequences, therefore reducing the immunogenicity.

IMGT notes:

(1)

The IGK V-J YTH34.5HL rearrangement is the following: IGKV22S7*01-IGKJ2-3*01.